1. Field of the Invention
The present invention relates to color photographic materials. More particularly, it relates to color photographic materials, which form images having a high maximum density, a low minimum density and improved gradation, and to a process for forming color images using such color photographic materials.
2. Description of the Prior Art
As the direct reversal emulsions, inner latent image type emulsions and solarization type emulsions have been generally known. The inner latent image type direct reversal emulsions have been described in U.S. Pat. Nos. 2,497,875, 2,588,982, 2,456,953, 3,761,276, 3,206,313, 3,317,322, 3,761,266, 3,850,637, 3,923,513, 3,736,140, 3,761,267 and 3,854,949, etc. The solarization type direct reversal emulsions have been described in The Theory of the Photographic Processes, pp. 261 to 297, edited by Mees (Macmillan Co., New York, 1942), and processes for preparing them have been described in British Pat. Nos. 443,245 and 462,730 and U.S. Pat. Nos. 2,005,837, 2,541,472, 3,367,778, 3,501,305, 3,501,306 and 3,501,307, etc.
Diffusible dye releasing redox compounds, namely, dye image forming substances which are originally non-diffusible and release a diffusible dye upon decomposition as a result of a reaction such as (1) hydrolysis and ring formation or (2) oxidation and hydrolysis (referred to as "DRR compounds") have been described in, for example, U.S. Pat. Nos. 3,932,381, 3,928,312, 3,931,144, 3,954,476, 3,929,760, 3,942,987, 3,932,380, 4,013,635 and 4,013,633, Japanese Patent Application (OPI) Nos. 113624/76 (The term "OPI" as used herein refers to a "published unexamined Japanese patent application"), 109928/76, 104343/76, 4819/77 and 149328/78 and Research Disclosure, pp. 68 to 74 (November, 1976) and the same journal No. 13024 (1975), etc.
It has been well known that an increase in minimum density occurs when a color diffusion transfer photographic material comprising a combination of the above-described direct reversal emulsion and DRR compound is developed using a black-and-white developing agent such as 3-pyrazolidinone derivatives. Alkyl hydroquinones have been used to decrease the minimum density as described in, for example, British Pat. Nos. 558, 258, 557, 750 (corresponding to U.S. Pat. No. 2,360,290), British Pat. Nos. 557,802 and 731,301 (corresponding to U.S. Pat. No. 2,701,197), U.S. Pat. Nos. 2,336,327, 2,403,721 and 3,582,333, German Patent Application (OLS) No. 2,505,016 (corresponding to Japanese Patent Application (OPI) No. 110337/75) and Japanese Patent Application (OPI) No. 4819/77. Similarly, U.S. Pat. No. 3,352,672 reports the use of 5-substituted tetrazoles and U.S. Pat. No. 3,637,387 reports the use of compounds releasing halogen ions to reduce minimum density.
In addition to the above, other techniques and compounds have been relied upon in the art to reduce the minimum density and obtain images of good gradation. In German Patent Application No. 2,427,183 and Japanese Patent Application (OPI) Nos. 8828/77 and 148122/77, it has been described to use compounds which release a development inhibitor by alkali hydrolysis. In Research Disclosure, No. 16631 (February, 1978), it has been described to use quinones. In German Patent Application No. 2,746,259, it has been described to add primary aliphatic amino acids or aliphatic acids and primary aliphatic amines to a developing solution. However, in the above-described processes, the minimum density is not sufficiently decreased or the maximum density is simultaneously decreased with the decrease in minimum density. Further, in some cases, the compounds themselves color and stain which increases minimum density.
In Research Disclosure, No. 15162 (November, 1976), hydroquinone compounds as disclosed in U.S. Pat. No. 3,379,529 issued to Porter et al which release a development inhibitor (referred to as DIR hydroquinone compounds) have been described for use in photographic materials for the color diffusion transfer process. The embodiments of this invention, however, can be contrasted with the Research Disclosure in the following regard. Namely, in this invention, the DIR compound having a specific structural formula indicated hereinafter is used in combination with DRR compounds in a specific location relationship. When such a DIR compound is employed in a specific location relationship, the effect of the invention (e.g., high maximum density, low minimum density and good gradation) can be obtained.